Shunts are often used as internal medical devices to drain aberrant fluids from different organs. Reference is first made to FIG. 1, which illustrates a CSF shunt, implanted into the cranial cavity of a child. The shunt head 10, shown on a larger scale in FIG. 2, consists of a hollow catheter 20, usually made of silicone, with a series of perforations 21, 22, along its length, the holes often having different sizes and different spacings, such that fluid accumulated round the shunt can drain through the holes into the tube, and away from the region from which the fluid has to be drained. The excess fluid is generally drained into a body cavity such as the abdomen. The shunt head may have length calibrations imprinted thereon, so that the physician can estimate how far it has been inserted into the cranial cavity. The shunt head is attached by means of a tubular connector 18 to a drain tube 12, which conveys the excess cerebral fluids typically into the patient's abdomen. The drain tube is generally implanted just beneath the skin, with access to the cranial region to be drained and into the abdominal cavity being achieved by means of small incisions 16 in the meninges and the peritoneum respectively. In order to allow the patient to grow from infanthood without the need for changing the shunt, the end section of the drain tube I 4 may be bundled up in the abdominal cavity, so that it can unravel as the child grows. Although CSF shunts are perhaps the most commonly used shunts, it is to be understood that such shunts could be applied to any other part of the body where the drainage of excess fluid is required, such as in urethral catheters, vesicostomy, peritoneal dialysis, and others. Furthermore, such shunts could also be used in industrial applications where it may be necessary to drain fluids from a remote inaccessible location.
Such prior art simple shunts generally have two major problems:
(i) the inlet apertures might get clogged, and
(ii) it may become infected.
When the shunt is clogged, an attempt to remove it from the body by surgery should be made. In cases where it is impossible to remove, another shunt may be placed in parallel to the malfunctioning one. When the shunt is infected it must be removed from the body by surgery. Surgeries of this kind are often high risk procedures.
The simple prior art shunt shown in FIGS. 1 and 2 have a significant drawback in that after some period of time inside the human body, living tissue growth may result in blockage of the holes by the tissue. This tissue is generally the main cause of shunt blockage. When trying to withdraw the shunt by surgery, the ingrown tissue may tear, causing intraventricular bleeding, which might be life threatening.
To avoid the risk of such bleeding, doctors sometimes prefer not to remove the shunt but to implant another one in addition to the original damaged or clogged one. This procedure includes surgery and the new shunt might also cause an infection. When a shunt is infected, it must be removed before any new device is inserted. In such a case, if the silicone tube needs to be removed, and if it is stuck to the choroid plexus, an open craniotomy and intraventricular operation needs to be performed in order to prevent intraventricular bleeding.
In order to avoid such complications, a number of self cleaning shunt heads have been proposed in the prior art. Many depend on back-flushing of the shunt head using the fluid within the tube. One such prior art shunt is shown in U.S. Pat. No. 5,584,314 to D. Bron, for “Self cleaning inlet head for a fluid.” The head is cleaned by manually pressing on a reservoir implanted subcutaneously thus causing a cleaning motion by means of the shunt fluid. However, the head of this shunt appears to be mechanically complex, which may result in reduced reliability in the long term.
In co-pending International Patent Application No. W02008/126087 for “Vibrating Robotic Crawler”, having one co-inventor with the present application, there is described an autonomous vibration driven device, for motion through a lumen utilizing an array of flexible fibers attached to the body of the device. In that publication, there is described one application of such a device for keeping the bore of shunts clear of obstructions. The vibrating robotic crawler is capable of crawling in tubes, and is ideal for opening occlusions in such shunts, often preventing the need for shunt revision procedures.
However, it does not relate to the problem of the blocking of the shunt fluid inlet holes themselves, which may become blocked by the ingrowth of living tissue, such as choroid plexus or by blood clots.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.